Method of unitizing packages by means of a stretchable adhesive tape

ABSTRACT

Means for unitizing objects, e.g., packages, through the use of a stretchable, detackifiable, pressure-sensitive adhesive tape. In the preferred embodiment, the tape comprises a highly extensible, substantially non-recoverable backing bearing on at least one major surface thereof a layer of pressure-sensitive adhesive. This tape has the dual capability of (1) being capable of being firmly bonded to a substrate and (2) being detackified after being stretched.

This is a continuation of U.S. application Ser. No. 07/731,341 filedJul. 19, 1991, now abandoned.

FIELD OF THE INVENTION

This invention relates to means for securing objects together forstorage, shipping, or other purposes.

DISCUSSION OF THE ART

In many manufacturing plants, products or packages are at some pointgrouped with other products or packages to facilitate handling, storage,and shipping. Such grouping is commonly referred to as "unitizing".Perhaps the most common form of unitizing is palletization. As aspecific facet of unitization, palletization becomes a process in whichthe unit load is joined with a pallet to provide for handling,primarily, with fork lift trucks. A palletized load must have verticalstrength and horizontal or lateral stability. The stacking strength of aload (particularly loads of products packaged in cartons or containers)depends on the pattern or layout of each tier. For most cases, a columnstack (one box directly on top of another) yields the greatest verticalstrength. The column stack, however, has little lateral stability.Interlocking patterns increase lateral stability at some sacrifice invertical strength. These patterns additionally can be used to optimizepallet space utilization. The end result of balancing vertical stackingstrength, lateral stability, and space utilization can be an array ofpallet patterns, requiring a different one for each product or packagebeing palletized.

Several equipment manufacturers have added a horizontal strappingsection to their palletizers to stabilize loads during the palletizingoperation. Besides saving space, cutting labor costs, and simplifyinghandling, strapping during palletizing is also effective for stabilizingextremely unstable loads before they must be handled. Usually two orthree strapped tiers will stabilize most loads, with many usersstrapping only the second layer from the top.

One means of providing lateral stability at low cost has been the use ofadhesives to bond the layers of the load together. Adhesives for thispurpose must have good shear strength to resist lateral forces thatwould cause a load to come apart. They must also have low tensilestrength so that the load can be disassembled without damaging theproduct or package. Steel and, more recently, plastic strappings havebeen used for securing unitized and palletized loads. The plastics, e.g.polypropylene, nylon, and polyester, have replaced steel in enoughapplications so that now 80% of the strapping used for generalpalletizing is plastic. Of the plastics, polyester has been the mostfrequently used replacement for steel strapping, on account of the highbreaking strength of the newer polyester products.

A few years ago, shrink wrapping of pallet loads generated considerableenthusiasm. While insuring load integrity, shrink wrapping also providedprotection from dust, dirt, water, and pilferage. In more recent years,however, shrink wrapping has lost some of its initial appeal because ofrising energy costs. The large ovens sometimes used for shrinking thefilms around pallet loads consume too much energy in securing theunitized loads and the resultant costs have caused shrink wrapping tolose ground to the more energy-efficient stretch wraps.

The major share of pallet stabilization is being accomplished withstretch wrap. The variety of available equipment for stretch wrappingruns from hand-held manual wrapping devices to automatic high-speedsystems.

One area of unitization that is becoming more and more popular isbundling. Lumber, sheets of insulation, and bags of pet food haveenjoyed successful bundling applications. Bundling has found applicationin a number of different industries, including the manufacture oflighting fixtures. Palletizing, unitizing, securing, wrapping, andbundling with strapping, adhesives, shrink wraps, or stretch wraps areactivities common to nearly every packaging and shipping department.

It would be desirable to find a wrapping or strapping material thatwould avoid the following problems:

(1) pull of fibers from the surface of containers on account ofaggressive, sticky adhesives;

(2) elimination of heating equipment needed to shrink wrapping material;

(3) elimination of additional mechanical devices to secure palletizedloads, e.g., clips to join the ends of strapping material;

(4) elimination of excessive amounts of waste material, e.g., usedstretch wrap;

(5) minimizing excessive looseness of strapping material, which resultsin movement of packages;

(6) minimizing excessive tightness of strapping material, which resultsin damaging packages; and

(7) prevention of air circulation about the unitized load in order tominimize moisture condensation.

SUMMARY OF THE INVENTION

This invention provides a means for unitizing objects, e.g., packages,through the use of a stretchable, detackifiable, pressure-sensitiveadhesive tape. In the preferred embodiment, the tape comprises a highlyextensible, substantially non-recoverable backing bearing on at leastone major surface thereof a layer of pressure-sensitive adhesive. Thistape has the dual capability of (1) being capable of being firmly bondedto a substrate and (2) being detackified after being stretched.

In order to unitize a group of objects, a small portion of the tape,preferably from a roll, is first applied to a first object, the tape, ifin a roll, is then simultaneously unwound, stretched to inducedetackification, and wrapped around the remaining objects; finally aportion of the unstretched tape is adhered to an object in the group toanchor the stretched, detackified tape. The tape can be easily removedmerely by releasing the adhering portions of the tape from the regionsof objects to which these portions are adhered.

The backing of the stretchable, detackifiable pressure-sensitiveadhesive tape preferably has a Young's modulus of at least about 2,500psi, more preferably at least about 3,000 psi, but less than about100,000 psi, most preferably between about 5,000 and about 30,000 psi.The backing preferably has a high tensile strength, a lengthwiseelongation at break of at least about 150%, more preferably at leastabout 200%, still more preferably at least about 600 to 800%, andpreferably has low recovery, e.g.,. less than about 50% elastic recoveryafter being stretched, more preferably less than about 30% elasticrecovery. If the tape is stretched up to its breaking point, the tapewill have low resiliency; if the tape is not stretched up to itsbreaking point, it will retain sufficient residual resiliency to applytension to the load of unitized objects, i.e., in the manner of a largerubber band. Unlike a rubber band, however, the tape preferably exhibitsa low degree of recovery. Tape having a relatively higher degree ofrecovery can be used if it is applied by power-driven machinery and ifit does not retackify upon recovery.

The layer of pressure-sensitive adhesive of the tape has sufficientshear strength and adhesive holding power to adhere to the small regionsof the objects to which the tape is attached. The holding power of theadhesive to any substrate is preferably both less than the cohesivestrength of the adhesive and less than the adhesion of the adhesive tothe backing, so that the adhesive layer or a portion thereof will notseparate from the backing when the backing is subjected to stretching.The adhesive layer is also preferably highly extensible. The adheredportion of the tape can be cleanly released from a surface to which itis adhered by stretching it at an angle of less than 35° from thesurface to which it is adhered.

The characteristic of detackification of the tape by means of stretchingprevents the tape from adhering to the surface of objects. This isimportant, as permanent adhesion would deface the surface of the objectupon removal of the tape therefrom. The amount of tape that must adhereto an object to provide sufficient anchorage for a strapping applicationcan constitute a relatively insignificant portion of the total amount oftape required for the application. The characteristic of stretchabilitycan allow a relatively small quantity of tape to be used for a givenunitizing application.

The characteristic of detackification upon being stretched allows thetape disclosed herein to be used for unitizing packages, particularlypackages contained on a pallet, for closing and securing singlepackages, and for securing bundles of loose articles, such as forexample, rods and sheets made of wood, metal, or fibrous materials. Ineffect, the tape can be used as a replacement for string, twine, orwire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a plurality of packages arranged intiers and having a single strip of stretchable, detackifiable,pressure-sensitive adhesive tape wrapped around one tier of packages.

FIG. 2 is a perspective view of a plurality of packages arranged intiers and having a single strip of stretchable, detackifiable,pressure-sensitive adhesive tape wrapped around each tier of packages.

FIG. 3a is a perspective view of the front of a plurality of packagesarranged in tiers and having a single strip of stretchable,detackifiable, pressure-sensitive adhesive tape wrapped around severaltiers of packages in a manner such that shifting of the packages isminimized.

FIG. 3b is a perspective view of the plurality of packages shown in FIG.3a, but with the arrangement rotated 90°.

FIG. 4a, 4b, and 4c are schematic views illustrating how thedetackifiable tape operates in the method of this invention.

FIG. 5 is a perspective view of a box closed and secured by a tapestretched according to the method of this invention.

DETAILED DESCRIPTION

A tape suitable for this invention is fully described in Assignee'scopending U.S. application Ser. No. 07/632,173, filed Dec. 20, 1990,incorporated herein by reference. However, tapes other than thatparticular tape are suitable for the method of this invention. Ingeneral, tape 10 comprises a backing bearing on at least one majorsurface thereof a layer of pressure-sensitive adhesive. The majorsurface of the backing not bearing the layer of pressure-sensitiveadhesive can optionally bear a layer of low-adhesion backsizecomposition.

Materials suitable for the backing of the tape useful in this inventioninclude highly extensible polymeric sheet materials having (1) a hightensile strength; (2) a lengthwise elongation at break of from about 50to about 1,500%, preferably from about 150 to about 800%, morepreferably from about 200 to about 800% still more preferably from about600 to about 800%; (3) substantial inelasticity, e.g., preferably havingless than about 50% elastic recovery after being stretched, morepreferably less than about 30% elastic recovery, still more preferablyless than about 20% elastic recovery; and (4) a Young's modulus of atleast about 2,500 psi, preferably at least about 3,000 psi, but lessthan about 100,000 psi, more preferably between about 5,000 and about30,000 psi. A suitable method for measuring the Young's modulus of amaterial is described in ASTM Designation D882-88, Standard Test Methodsfor Tensile Properties of Thin Plastic Sheeting. If the Young's modulusis too low, the tape loses its plastic character and becomes rubbery.

Representative examples of materials suitable for the backing of thetape of this invention include polyolefins, such as polyethylene,including high density polyethylene, low density polyethylene, linearlow density polyethylene, and linear ultra low density polyethylene,polypropylene, and polybutylenes; vinyl copolymers, such as polyvinylchlorides, both plasticized and unplasticized, and polyvinyl acetates;olefinic copolymers, such as ethylene/methacrylate copolymers,ethylene/vinyl acetate copolymers, acrylonitrile/butadiene/styrenecopolymers, and ethylene/propylene copolymers; acrylic polymers andcopolymers; and combinations of the foregoing. Mixtures or blends of anyplastic or plastic and elastomeric materials such aspolypropylene/polyethylene, polyurethane/polyolefin,polyurethane/polycarbonate, polyurethane/polyester, can also be used.Backings are typically in the form of single or multi-layer films.Backings are preferably selected from polyethylene and polypropylenefilms, with the most preferred materials being linear low density andultra low density polyethylene films.

Backings can be made by any known method of film forming, such as, forexample, extrusion, co-extrusion, solvent casting, foaming, non-woventechnology, and the like. The backing can have any thickness so long asit possesses sufficient integrity to be processable and handleable, withthicknesses preferably ranging from about 10 micrometers to 750micrometers. Backings having thicknesses lower than about 10 micrometersare not preferred for aggressive adhesives. Backings having thicknesseshigher than about 750 micrometers tend to require stretching forces thatare higher than desired, thereby making applications more difficult,except by power driven machinery.

The adhesive of the adhesive layer can comprise any pressure-sensitiveadhesive, with the particular adhesion properties being dependent on theuse of the tape, with the preferred adhesion properties generallyranging from about 4 N/dm to about 200 N/dm, preferably from about 25N/dm to about 100 N/dm, at a peel angle of 180°, measured according toPSTC-1 and PSTC-3 and ASTM Designation D903-83 at a peel rate of 12.7cm/min.

Pressure-sensitive adhesives suitable for this invention includetackified rubber adhesives, such as natural rubber, olefins, silicones,polyisoprene, polybutadiene, polyurethanes, styrene-isoprene-styrene andstyrene-butadiene-styrene block copolymers, and other elastomers; andtackified or untackified acrylic adhesives such as copolymers ofisooctylacrylate and acrylic acid, which can be polymerized byradiation, solution, suspension, or emulsion techniques. The mostpreferred adhesives are tackified block copolymers. For some purposes,adhesives that are incapable of providing enhanced adhesion over timeare desired, so that removal of the tape by peeling at a less thanoptimum angle will not excessively deface the package.

The thickness of the adhesive layer can range from about 15 micrometersto about 1,000 micrometers, preferably from about 25 micrometers toabout 400 micrometers. In this preferred range of thicknesses, thethicker layers will detackify less than will thinner layers.Alternatively, the coating weight of the adhesive in the adhesive layercan range from about 1/2 grain/24 sq. in. to about 50 grains/24 sq. in.,preferably from 3 grains/24 sq. in. to 15 grains/24 sq. in.

As the tape is stretched, the adhesive must detackify. As used herein,the term "detackification" means reduction of tack and adhesion, asmeasured by the Pressure-Sensitive Tack Test, which will be described indetail below. As a practical matter, upon stretching, tack is preferablyreduced by at least 10%, more preferably by at least 25%, and even morepreferably by at least 50%. It is believed that the adhesive detackifiesbecause the coating weight of the adhesive layer decreases on account ofthe increased area of the surface of the backing. Surprisingly, thelevel of detackification exceeds what would have been expected merelyfrom a decrease in coating weight per unit area.

The tape of this invention can be produced by any conventional methodfor preparing pressure-sensitive adhesive tapes. For example, theadhesive can either be directly coated onto the backing, or it can beformed as a separate layer and then later laminated to the backing. Insome cases, in order to improve adhesion of the adhesive layer to thebacking, the backing can be pretreated prior to the coating step or thelaminating step in one or more of the following ways: corona discharge,plasma discharge, flame treatment, electron beam irradiation,ultraviolet radiation, acid etching, or chemical priming. Suchpretreatments can be carried out with or without reactive chemicaladhesion promoters such as hydroxyethyl acrylate or hydroxyethylmethacrylate, or other reactive species of low molecular weight. Coronadischarge pretreatment is generally preferred if a polymeric filmbacking is used.

If it is desired to dispense the tape from a roll, it is preferred thatthe major surface of the backing not bearing a pressure-sensitiveadhesive bear a layer of a low-adhesion backsize composition thereon toallow ease in unwinding. Alternatively, the layer of pressure-sensitiveadhesive can be covered with a release liner. Low-adhesion backsizecomposition suitable for the tape useful in this invention can beselected from those known in the art, such as, for example, thosedescribed in U.S. Pat. Nos. 2,532,011; 4,279,717; 4,961,963; 4,968,766;and 4,342,815, all of which are incorporated herein by reference.

In one of the simplest embodiments, as shown in FIG. 1, a tape 10 can bewrapped around a tier of objects, e.g., packages 12, that are resting onone or more tiers of objects, e.g., packages 14. This simple embodimentwould be expected to be most useful for light handling, e.g., moving apallet a short distance at a low rate of speed, as in a warehouse.

In an extension of this embodiment, as shown in FIG. 2, a tape 20 can bewrapped around a tier of objects, e.g., packages 22, that are resting onone or more tiers of objects, e.g., packages 24, and the second tier ofobjects, e.g., packages 24, can be wrapped by a second strip of tape 26.Additional strips of tape 28, 30, 32, 34 can be used to wrap additionaltiers of objects, e.g., packages 36, 38, 40, 42.

In a more complex embodiment, as shown in FIG. 3a and FIG. 3b, a tape 50can be wrapped in a crossing pattern around a group of objects, e.g.,packages 52, arranged in a plurality of tiers. This pattern providesequal and counteracting forces that stabilize the objects, therebypreventing them from shifting when exposed to vibrational forces. Thispattern would be expected to be effective for severe handling, e.g.,over-the-road trucking, long distances at a high rate of speed.

With respect to the arrangement of objects shown in FIGS. 3a and 3b, thematerial handler can attach a portion of the tape 50 to a package 52 atpoint A. The portion of the tape should be wrapped around a corner ofthe package 52 so that subsequent stretching of the tape 50 will notcause the tape to release from the surface of the package 52. Tape 50 isthen stretched and guided so as to contact, in sequence, a secondpackage 52 at point B, a third package 52 at point C, a fourth package52 at point D, the first package 52 at point A, a fifth package 52 atpoint E, a sixth package 52 at point F, a seventh package 52 at point G,an eighth package 52 at point H, the fifth package 52 at point E, aninth package 52 at point J, the fourth package 52 at point D, a tenthpackage 52 at point K, an eleventh package 52 at point L, the thirdpackage 52 at point C, the eighth package 52 at point G, the tenthpackage 52 at point K, the second package 52 at point B, the ninthpackage 52 at point J, a twelfth package 52 at point M, the eighthpackage 52 at point H, the eleventh package 52 at point L, the sixthpackage 52 at point F, the twelfth package 52 at point M, and the firstpackage 52 at point A.

The tape is preferably applied to the packages on a pallet undertension, the tape thereby retaining some of its elastomeric properties.In effect, the tape acts as though it were a large rubber band. However,the tape preferably exhibits much less recovery than a rubber band.

It is within the scope of this invention to include the pallet itself asan object, i.e., the tape can be wrapped around both the objects to bestored and the pallet bearing them.

The detackification characteristic of the tape allows the tape to beremoved from the objects without damaging the surfaces of the objects.It has also been found that stretching the tape also increases thetensile strength of the tape.

Referring to FIGS. 4a, 4b, and 4c, it can be seen how a tape 60 having abacking 62 and a layer of pressure-sensitive adhesive 64 can be pulledand stretched without detaching from an object 66 prematurely. If thetape 60 is pulled at an angle of less than 35° from the horizontal, asshown in FIG. 4a, the portion of the tape 60 adhered to surface 68 ofthe object 66 will release and the portion of the tape 60 will no longeradhere to surface 68. If the tape 60 is pulled at an angle of from about35° to about 45° from the horizontal, as shown in FIG. 4b, the portionof the tape 60 adhered to surface 68 will not significantly detackifyand the portion of the tape 60 will remain adhered to surface 68. If thetape 60 is pulled at an angle of greater than 45° from the horizontal,as shown in FIG. 4c, the portion of the tape 60 adhered to surface 68will not detackify and the portion of the tape 60 will remain adhered tosurface 68. Alternatively, the users of the tape can exercise sufficientcare so as to stretch the tape without removing from the surface of theobject the portion of the tape adhered thereto.

The volume of tape required to unitize a group of objects isconsiderably less than the amount of shrink wrap or stretch wraprequired to unitize those objects. Accordingly, less solid wasterequiring disposal is generated.

The method of this invention can be used to unitize a plurality ofcontainers or other objects even if they are not disposed or arranged ina plurality of tiers on a pallet or other type of platform.

The method of this invention can also be used to wrap and secure asingle object, e.g., a box 70, with the tape 72 described herein.Referring to FIG. 5, a small piece 74 of the tape 72, as from a roll, isadhered to surface 76 of the box 70 at point X. The tape 72 is thenslowly unwound from the roll (not shown) and simultaneously stretched todetackify the portion of the tape 72 not adhering to the box 70 at pointX. At the same time that the tape 72 is unwound, it is wrapped aroundthe box 70 so as to close it. After the box 70 is wrapped as desired, asmall portion 78 of the tape 72 is unwound, but not stretched. Thisportion is attached to the box 70 at point Y to secure the tape 72around the closed box 70. Significant adhesion between the tape 72 andthe box 70 is obtained only at points X and Y. When the tape 72 isremoved from the box 70, the area of potential damage to the box islimited to points X and Y. Wrapping configurations other than that shownin FIG. 5 can be used to close and secure individual boxes.

Other methods involving the tape described herein include masking,sealing, and insulating.

In a number of applications, e.g., in the automotive area, masking iscritical, as it is necessary to conform to irregularities of the surfaceto be masked. In this case, the stretching capability can be used toachieve the necessary conformity. Typically, stretching is carried outat a fairly low rate, e.g., 10 to 20%, at those places where conformityis needed.

In the area of plumbing, tapes can be used to wind around a thread of afirst tube that is to be connected to a second tube. Instead ofemploying a polytetrafluoroethylene connector, the stretchable tape canbe used to generate a very thin layer for the sealing of the thread.

For low voltage electrical applications, the stretchable tape can alsobe used for insulation purposes.

Another useful application for the tape of this invention is thewrapping of a plurality of cables by stretching and wrapping the tape ofthis invention about the cables in a spiral configuration.

Adhesion of the tape to an object in the stretched area of the tape canbe controlled by specifying the degree of stretching or by specifyingthe appropriate adhesive.

While not exhibiting as many useful functions as the tape previouslydescribed, tapes having backings bearing layers of adhesive on bothmajor surfaces thereof can also be used in the method of this invention.

The following non-limiting examples further illustrate the means of thepresent invention.

TEST METHODS Pressure-Sensitive Tack Test

A one inch by one inch strip of the tape is adhered to an annular ringhaving a weight of 78.5 g. A stainless steel test probe (SS) or apolyethylene test probe (PE)(both of which are 3/8 inch in diameter) israised through the center of the annular ring at a speed of 1 cm/sec andbrought into contact with the adhesive-bearing surface. After a dwelltime of one second, the probe is separated from the adhesive-bearingsurface and the maximum force needed to separate the probe from theadhesive-bearing surface is measured and recorded. Additional details ofthis test are set forth in ASTM Designation D2979-82.

180° Peel Adhesion to Stainless Steel

A sample of tape having dimensions one inch wide by 10 to 12 inches longis adhered to a stainless steel (AISI 302 or 304) test panel havingdimensions of at least two inches wide by five inches long by 1/16 inchthick along the centerline of the test panel so that from five to seveninches of the sample of tape extend beyond the edge of the test panel.The sample of tape is rolled once in each direction with a five poundroller. An end of the sample of the tape not in contact with the testpanel is doubled back and an approximately one inch portion of it ispeeled from the test panel. The end of the panel is clamped in the lowerjaw of the tensile tester. The end of the sample of tape is doubled overto form a tab. This tab is clamped into the upper jaw of the tensiletester. The jaws are separated at a rate of 12 in/min, the averageadhesion value being noted. Additional details of this test are setforth in "Test Methods for Pressure-Sensitive Tapes", Pressure-SensitiveTape Council, Glenview, Illinois, 9th Edition, as PSTC-3.

180° Peel Adhesion to Fiberboard

This test is carried out the same way as the 180° Peel Test, withexception that the test surface is Mosinee 696-C paper (available fromMosinee Paper Corp., Mosinee, Wisconsin) attached to the entire surfaceof one side of the stainless steel test panel by means of a doublecoated tape.

180° Peel Adhesion to Corrugated Sheet

This test is carried out the same way as the 180° Peel Test withexception that the test surface is a two inches wide by five inches longby 0.165 inch thick, 200 # Kraft Faced Corrugated Box material, with theflutes running in the lengthwise direction.

Mechanical Handling of Unitized Load

Boxes made of corrugated sheet and having the dimensions 101/2 inches by121/2 inches by 151/4 inches and containing 12 to 15 pounds of sand fordunnage were stacked in a three by three by seven box configuration on astandard 42 inch by 48 inch pallet. The projections from a lift truckequipped with forks can engage the pallet from any direction, i.e.,front, back, left side, right side. Using a lift truck equipped withforks, the operator engages, lifts, and transports the pallet through anL-shaped test course at a walking speed not to exceed five ft/sec. TheL-shaped test course includes a 10 to 111/2 feet wide aisle with a 90°turn and an acceleration/deceleration zone. The pallets allow accessfrom any direction and are tested in directions that are perpendicularto each other, e.g., front and right side. Additional details on thistest are set forth in ASTM Designation D1083-88.

Vibration Test

A unitized pallet as described in the Mechanical Handling of UnitizedLoad Test was loaded onto a Vibration Test Machine. The Vibration TestMachine consisted of a flat horizontal test surface that distributed anapplied vibration uniformly throughout a platform. The platform wasdriven to move only vertically in a sinusoidal motion. The frequency andamplitude of the motion were variable, controllable, and covered a rangeof acceptable breadth. The test cycle consisted of a sweep of frequencystarting at three Hz. and sweeping to 100 Hz. and then back to three Hz.Separate sweeps were run at acceleration levels from 0.1 g to 0.5 g.Additional details of this test are set forth in ASTM DesignationD3580-89.

EXAMPLE I

A series of tapes employing a block copolymer based pressure-sensitiveadhesive composition were prepared to illustrate adhesion to varioussurfaces, and fiber pull from the surfaces of various packagingmaterials. Each tape of the series was prepared by coating one majorsurface of a 5 mil linear low density polyethylene (LLDPE) backing witha tackified pressure-sensitive adhesive. The adhesive was astyrene-isoprene-styrene-based block copolymer ("Kraton" 1107) tackifiedwith hydrocarbon resin ("Wingtack Extra").

The formulation for the adhesive of this example was similar to thatdescribed in U.S. Pat. No. 3,239,478, incorporated herein by reference,and is as follows:

    ______________________________________                                        Ingredient           Amount (phr)                                             ______________________________________                                        Styrene-isoprene-styrene                                                                           100                                                      block copolymer ("Kraton"                                                     1107, Shell Chemical Co.)                                                     Hydrocarbon resin tackifier                                                                        100                                                      ("Wingtack Extra", The                                                        Goodyear Tire and Rubber Co.)                                                 Antioxidant ("Irganox" 1076,                                                                       1.5                                                      Ciba-Geigy Corp.)                                                             Antioxidant ("Cyanox LTDP",                                                                        1.5                                                      American Cyanamid Co.)                                                        ______________________________________                                    

The low adhesion backsize composition comprised a copolymer of vinylN-octadecyl carbamate and vinyl acetate, which was described in U.S.Pat. No. 2,532,011, incorporated herein by reference.

The backing had been corona treated on both major surfaces thereof. Alow-adhesion backsize composition was applied to the major surface ofthe backing not bearing the adhesive. The coating weight of adhesive ofeach of the unstretched and stretched tapes of the series, in grains per24 sq. in., are set forth in Table 1. The tape exhibited 720% elongationwhen stretched by hand.

                  TABLE 1                                                         ______________________________________                                                     Coating weight                                                                            Coating weight                                       Sample no.   (unstretched)                                                                             (stretched)                                          ______________________________________                                        1            2.1         1.4                                                  2            3.7         1.5                                                  3            4.9         2.0                                                  4            5.7         2.2                                                  5            8.4         3.6                                                  6            9.2         4.3                                                  ______________________________________                                    

The data in Table 1 indicate that stretching to ultimate yield can givea 2.3 times reduction (approximately) in adhesive coating weight perunit area. The reduction is believed to result from an increase in thesurface area of the backing. This reduction results in a reduction intack and adhesion.

Adhesion, in oz. per in., to corrugated paperboard is set forth in Table2.

                  TABLE 2                                                         ______________________________________                                        Sample Adhesion (oz./in.)                                                                             Fiber pull (%)                                        no.    (unstretched)                                                                            (stretched)                                                                             (unstretched)                                                                          (stretched)                              ______________________________________                                        1      16.3       1.0       100      0                                        2      17.7       3.7       100      0                                        3      21.3       6.0       100      0                                        4      19.7       7.0       100      0                                        5      18.7       10.7      100      0                                        6      19.0       11.3      100      0                                        ______________________________________                                         Pressure-sensitive tack, in g/0.1 sq. in., is set forth in Table 3.

                  TABLE 3                                                         ______________________________________                                        Tack - SS probe     Tack - PE probe                                           Sample (g/0.1 sq. in.)  (g/0.1 sq. in.)                                       no.    (unstretched)                                                                            (stretched)                                                                             (unstretched)                                                                          (stretched)                              ______________________________________                                        1      1319       276        909     125                                      2      1381       494        977     301                                      3      1832       793       1273     254                                      4      2048       813       1424     370                                      5      2232       1210      1645     319                                      6      2156       969       1501     269                                      ______________________________________                                    

In Table 4, both adhesion to the surface of fiberboard and fiber pullfrom the surface of fiberboard are set forth for the tape.

                  TABLE 4                                                         ______________________________________                                        Sample Adhesion (oz./in.)                                                                             Fiber pull (%)                                        no.    (unstretched)                                                                            (stretched)                                                                             (unstretched)                                                                          (stretched)                              ______________________________________                                        1      14         10        97       35                                       2      14         14        93       73                                       3      15         15        93       97                                       4      15         13        97       36                                       5      19         15        95       60                                       6      15         16        95       87                                       ______________________________________                                    

EXAMPLE II

A series of tapes employing an acrylate-based pressure-sensitiveadhesive composition was prepared to illustrate adhesion to varioussurfaces, and fiber pull from the surfaces of various packagingmaterials. Each tape of the series was prepared by coating one majorsurface of a 4 mil LLDPE backing with a tackified pressure-sensitiveadhesive. The adhesive was an acrylate adhesive comprising 90 parts byweight isooctyl acrylate and 10 parts by weight acrylic acid preparedaccording to Re. 24,906 (Ulrich), incorporated herein by reference. Thebacking had been corona treated on both major surfaces thereof. Alow-adhesion backsize composition was applied to the major surface ofthe backing not bearing the adhesive. The low-adhesion backsizecomposition was of the type described in Example 1. The coating weightof adhesive of each of the unstretched and stretched tapes of theseries, in grains per 24 sq. in., are set forth in Table 5.

                  TABLE 5                                                         ______________________________________                                                     Coating weight                                                                            Coating weight                                       Sample no.   (unstretched)                                                                             (stretched)                                          ______________________________________                                        1             3.7        1.3                                                  2             6.0        1.6                                                  3            10.5        3.0                                                  4            12.8        2.7                                                  ______________________________________                                    

The data in Table 5 indicate that stretching to ultimate yield can givea 3.7 times reduction (approximately) in adhesive coating weight perunit area. The reduction is believed to result from an increase in thesurface area of the backing.

Both adhesion to the surface of corrugated paperboard and fiber pullfrom the surface of corrugated paperboard are set forth in Table 6.

                  TABLE 6                                                         ______________________________________                                        Sample Adhesion (oz./in.)                                                                             Fiber pull (%)                                        no.    (unstretched)                                                                            (stretched)                                                                             (unstretched)                                                                          (stretched)                              ______________________________________                                        1      15.3        6.7       98      12                                       2      15.5        8.5       97      20                                       3      14.0       13.2      100      44                                       4      15.2       15.0      199      94                                       ______________________________________                                    

Both adhesion to the surface of fiberboard and fiber pull from thesurface of fiberboard are set forth in Table 7.

                  TABLE 7                                                         ______________________________________                                        Sample Adhesion (oz./in.)                                                                             Fiber pull (%)                                        no.    (unstretched)                                                                            (stretched)                                                                             (unstretched)                                                                          (stretched)                              ______________________________________                                        1      14.7        9.3       75       5                                       2      14.2       13.7      100      100                                      3      13.5       15.0      100      100                                      4      14.7       15.7      199       77                                      ______________________________________                                    

The data in the foregoing tables show that there is a greater decreasein adhesion than would have been expected from a mere reduction inadhesive coating weight. For example, the adhesion and tack of a tapehaving a stretched coating weight of 2.0 to 2.2 grains per 24 sq. in.(i.e., Sample nos. 3 and 4) is significantly lower than the adhesion andtack of a tape having an unstretched coating weight of 2.1 grains per 24sq. in. (i.e., Sample no. 1). A decrease in adhesion correlates directlywith a reduction in tack, i.e., detackification.

EXAMPLE III

A group of containers was unitized by means of the stretchable tapedisclosed herein in the manner shown in FIG. 3. The tape was applied byhand at a stretch ratio of 6 to 1. For the purpose of comparison, asecond group of containers, identical to the first group, was unitizedby means of stretch wrap, also applied by hand. Both groups of unitizedcontainers were subjected to the mechanical handling test and thevibration (table) test. The load displacement for each type of wrappingwas similar, and each type of wrapping was deemed to be adequate for usein a manufacturing facility.

The tape and stretch wrap were then removed from the unitizedcontainers, and the scrap tape and scrap wrap were weighed. The stretchwrap weighed 7.4 ounces. The stretch tape weighed 2.3 ounces. Thus, theuse of tape resulted in a 70% reduction in waste.

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention, and it should be understood that thisinvention is not to be unduly limited to the illustrative embodimentsset forth herein.

What is claimed is:
 1. A method of unitizing at least two objects that are arranged in one or more tiers, at least one of said tiers comprising at least one object, said method comprising the steps of:(1) providing a stretchable, detackifiable pressure-sensitive adhesive tape having (1) a backing having a Young's modulus of at least about 2,500 psi but less than about 100,000 psi, a lengthwise elongation at break of at least about 150% and low recovery, (2) said backing bearing a layer of pressure-sensitive adhesive thereon; (2) adhering a first small portion of said tape to a small portion of one of said objects; (3) stretching said tape sufficiently to detackify the portion thereof not adhered to said one of said objects; (4) wrapping said detackified portions of said tape around at least two of said objects; and (5) adhering a second portion of said tape to a small portion of one of said objects, whereby said objects are capable of resisting mechanical handling and vibration of said arranged objects.
 2. The method of claim 1, wherein said objects are arranged in at least two tiers.
 3. The method of claim 2, wherein said tape is wrapped around all of said objects on at least one of said tiers.
 4. The method of claim 1, wherein said objects comprise packages having at least six sides.
 5. The method of claim 1, wherein said tape is wrapped in a direction substantially parallel to the plane formed by the uppermost surfaces of said objects.
 6. The method of claim 1, wherein said tape is wrapped in a direction substantially non-parallel to the plane formed by the uppermost surfaces of said objects.
 7. The method of claim 1, wherein said tape is wrapped in both a direction substantially parallel to the plane formed by the uppermost surfaces of said objects and a direction substantially non-parallel to the plane formed by the uppermost surfaces of said objects.
 8. The method of claim 1, wherein at least one stretched and wrapped portion of said tape crosses over at least another stretched and wrapped portion of said tape.
 9. A method of closing and securing a package comprising the steps of:(1) providing a stretchable, detackifiable pressure-sensitive adhesive tape having (i) a backing having a Young's modulus of at least about 2,500 psi but less than about 100,000 psi, a lengthwise elongation at break of at least about 150% and low recovery, (2) said backing bearing a layer of pressure-sensitive adhesive thereon; (2) adhering a first small portion of said tape to a small portion of said package; (3) stretching said tape sufficiently to detackify the portion thereof not adhered to said package; (4) wrapping said detackified portion at least partially around said package; and(5) adhering a second small portion of said tape to a small portion of said package, whereby said package is capable of remaining closed and secured.
 10. The method of claim 8, wherein said package has at least six sides.
 11. A method of unitizing a plurality of objects comprising the steps of:(1) providing a stretchable, detackifiable pressure-sensitive adhesive tape having (1) a backing having a Young's modulus of at least about 2,500 psi but less than about 100,000 psi, a lengthwise elongation at break of at least about 150% and low recovery, (2) said backing having a layer of pressure-sensitive adhesive thereon; (2) adhering a first small portion of said tape to a small portion of at least one of said objects; (3) stretching said tape sufficiently to detackify the portion thereof not adhered to said object; (4) wrapping said detackified portion of said tape around said plurality of said objects; and (5) adhering a second portion of said tape to a small portion of at least one of said objects, whereby said plurality of said objects is unitized in the form of a bundle. 